The rapid introductin of new medical diagnostic technologies into the health care system has often resulted in proliferation of the technology and its acceptance without sufficient data concerning actual usefulness. This grant request proposes to evaluate the impact of cardiovascular nuclear medicine studies (CVNMS) on clinical patient management to study referral patterns for these procedures, to describe a subgroup of patients for whom such procedures are likely to have maximum impact, and to create decision trees for appropriate ordering of CVNMS. Two thousand patients will be enrolled who are referred for perfusion or wall motion studies at 3 hospitals in the Bronx-the Hospital of the Albert Einstein College of Medicine, Montefiore Hospital, and Bronx Municipal Hospital. The Nuclear Medicine Divisions at these hospitals are all under the Unified Department of Nuclear Medicine at AECOM, and thus there is uniformity in procedures and interpretations. These hospitals represent more than half the care and all of the cardiac tertiary care in the borough of 1.2 million people. Medical charts will be abstracted to determine patient status leading to CVNMS referral and patients will be examined by a cardiologist immediately prior to CVNMS to determine current cardiac clinical status. An expert cardiologist panel will be constituted, representative of cardiologists in academic medicine, clinical practice, and at various amounts of time post training. The panel will be asked to recommend one of the several options for clinical management having all the information above but without CVNMS results (pre-test panel) and again having CVNMS results (post-test panel). Patients will be followed 3 & 12 months post-CVNMS to determine actual clinical management. Relationships will be analyzed among referring physician's assessments, pre and post test panel recommendations, and actual patient management and outcome. Sensitivity and specificity will be determined for subset of patients who undergo catheterization or surgery. The broad demographic diversity of the populations served by the study hospitals as well as the professional diversity of the referring physicians will serve to make the results widely generalizable.